contrib: ffmpeg: fix availability #if test

It's available in macOS 10.13, not macOS 13.0 [^1].
The __builtin_available() is correct but not the #if around it.

[^1]: https://developer.apple.com/documentation/videotoolbox/vtcopysupportedpropertydictionaryforencoder(width:height:codectype:encoderspecification:encoderidout:supportedpropertiesout:)

contrib/src/ffmpeg/0011-avcodec-videotoolboxenc-disable-calls-on-unsupported.patch

@@ -23,7 +23,7 @@ index da7b291b03..6b263ee6e9 100644
  
 -#if defined (MAC_OS_X_VERSION_10_13) && (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_13)
 -    if (__builtin_available(macOS 10.13, *)) {
-+#if (TARGET_OS_OSX    && defined(__MAC_13_0)    && __MAC_OS_X_VERSION_MAX_ALLOWED  >= __MAC_13_0)     || \
++#if (TARGET_OS_OSX    && defined(__MAC_10_13)   && __MAC_OS_X_VERSION_MAX_ALLOWED  >= __MAC_10_13)    || \
 +    (TARGET_OS_IOS    && defined(__IPHONE_11_0) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)  || \
 +    (TARGET_OS_TV     && defined(__TVOS_11_0)   && __TV_OS_VERSION_MAX_ALLOWED     >= __TVOS_11_0)
 +    if (__builtin_available(macOS 10.13, iOS 11, tvOS 11, *)) {